According to current scientific research into sleep, there are two major stages of sleep: rapid eye movement (“REM”) sleep, and non-REM sleep. First comes non-REM sleep, followed by a shorter period of REM sleep, and then the cycle starts over again.
There are three stages of non-REM sleep. Each stage can last from 5 to 15 minutes. A person goes through all three stages before reaching REM sleep.
In stage one, a person's eyes are closed, but the person is easily woken up. This stage may last for 5 to 10 minutes. This stage is considered light sleep.
In stage two, a person is in light sleep. A person's heart rate slows and the person's body temperature drops. The person's body is getting ready for deep sleep. This stage is also considered light sleep.
Stage three is the deep sleep stage. A person is harder to rouse during this stage, and if the person was woken up, the person would feel disoriented for a few minutes. During the deep stages of non-REM sleep, the body repairs and regrows tissues, builds bone and muscle, and strengthens the immune system.
REM sleep happens 90 minutes after a person falls asleep. Dreams typically happen during REM sleep. The first period of REM typically lasts 10 minutes. Each of later REM stages gets longer, and the final one may last up to an hour. A person's heart rate and respiration quickens. A person can have intense dreams during REM sleep, since the brain is more active. REM sleep affects learning of certain mental skills.
Even in today's technological age, supporting healthy sleep is relegated to the technology of the past such as an electric blanket, a heated pad, or a bed warmer. The most advanced of these technologies, an electric blanket, is a blanket with an integrated electrical heating device which can be placed above the top bed sheet or below the bottom bed sheet. The electric blanket may be used to pre-heat the bed before use or to keep the occupant warm while in bed. However, turning on the electric blanket requires the user to remember to manually turn on the blanket, and then manually turn it on. Further, the electric blanket provides no additional functionality besides warming the bed.